This invention relates to a method and apparatus for making polymeric bristle subassemblies having a base string with polymeric filament bristles attached thereto and also to polymeric bristle subassemblies wherein the polymeric filament bristles are attached to each other without the presence of a base string.
Various methods for making elongated pile articles having a support strand or base string with a plurality of yarn bundles attached thereto that are useful in making carpet are shown in Mokhtar et al U.S. Pat. No. 5,470,629 issued Nov. 28, 1995, Edwards et al U.S. Pat. No. 5,547,732 issued Aug. 20, 1996, Mokhtar et al U.S. Pat. No. 5,498,459 issued Mar. 12, 1996, Edwards et al U.S. Pat. No. 5,472,762 issued Dec. 5, 1995 and Agreen et al WO 97/06003 published Feb. 20, 1997. These processes require a base string or support strand of a polymeric filament to move the wrap of yarn or filament along a mandrel as it is being processed to form the article. In a preferred ultrasonic bonding method for assembling these articles, one limitation of the method is that the bonding device must deliver vibrational energy through the wrap of yarns or filaments to the contact interfaces with the support strand to generate heating and partial melting of the strand and/or wrap. However, since the mass cross-sections of the yarns or filaments of the wrap are commonly smaller than the support strand cross-section, the bonding energy delivered to the interface of the wrap and the support strand must be controlled precisely within a given bonding window to produce surface melting at the interface of the wrap and the support strand while avoiding sufficient bulk heating in the wrap of yarns or filaments to damage or sever them. A wrap of small diameter yarns or filaments may exhibit narrow or even a nonexistent bonding window that results in an unstable or unsatisfactory process. Another limitation of these processes is that the support strand must maintain sufficient strength during the partial melting in the bonding step to transport the article through the process. The support strand must have a large enough cross-section or have a sheath/core structure with a core of a significantly higher melting material that it will not break under the tension and melting which occur during the process.
A process and apparatus are needed in which the requirements of the support strand or base string are reduced allowing for the use of a variety of sizes and types of base strings to form bristle subassemblies.
A continuous method for making a polymeric bristle subassembly using the steps of
(1) continuously forming a wrap of polymeric filaments by wrapping at least one filament around the axis of at least a three sided mandrel having a moving cable support on each corner running the length of the mandrel on the exterior corner of the mandrel capable of supporting and moving the polymeric filaments of the wrap along at least a portion of the length of the mandrel;
(2) feeding at least one base string outside of the wrap of polymeric filaments to a selected portion of the mandrel as required to form the subassembly, such as the corner or side of the mandrel, while the polymeric filaments of the wrap are being moved along at least a portion of the length of the mandrel;
(3) bonding the base string and the polymeric filaments of the wrap together by simultaneously pressing the base string in contact with the filaments of the wrap and applying energy to the base string and the polymeric filaments of the wrap; and
(4) cutting the polymeric filaments of the wrap at a point downstream of where the polymeric filaments of the wrap are bonded with the base string to form at least one bristle subassembly having at least one row of filament segments connected to at least one base string.
An apparatus for making the subassemblies is also part of this invention. Other aspects of this invention are a continuous method of making a bristle subassembly wherein the base string is omitted and the filaments of the wrap are bonded to each other through the use of an energy source, or the use of a polymeric bead to bond the filaments together or use of a solvent or an adhesive to bond the polymeric filaments of the wrap together to form a bristle subassembly.